L-carnitine has a variety of physiological functions, which the basic one is to “transport” long-chain fatty acids into mitochondria via mitochondrial membrane where the β oxidation happens. L-carnitine is essential to fatty acid metabolism that once the synthesis of carnitine is blocked in body, or carnitine is degraded or excreted excessively, or the function of carnitine transferase decreases or losses, disturbance of lipid metabolism occurs which affects energy supply and leads to many diseases. Typical extraction method for natural L-carnitine is extracting from beef which is reported by Cater in 1952. However because the absolute content of L-carnitine is very low in meat, and the choline existing in gravy which is very similar in structure makes it is difficult to separate them, the direct extracting method is complicated, with low yield and high price. Therefore, it is not easy to get abundant natural L-carnitine.
Currently, L-carnitine for medicinal use is usually synthesized artificially. Usually, separation of racemic compounds is used for L-carnitine synthesis. The raw materials are cheap and easy to get, the process is easy to industrialize. However, because the defects of traditional chemical resolution, D-isomer can not be removed completely, the synthetic L-carnitine is not absolutely laevorotatory, but contains D-carnitine.
Natural carnitine is L-carnitine, and only L-carnitine is physiological active is a competitive inhibitior of carnitine acetyl transferase (CAT) and carnitine palmityl transferase (PTC). Therefore about 10% patients suffered myasthenia gravis after taking the DL-carnitine (Martindale: the Extra Pharmacopoeia (33th): 1356). Therefore taking drug safety into consideration, it's necessary to strictly control the content of the D-carnitine in the chemical synthetic process.
Currently, the content of D-Carnitine is detected by specific rotation which is lack of accuracy. In order to detect accurately the content of D-carnitine in L-carnitine products, and provide much safer and more effective drugs, health products and food, it is necessary to develop a method to detect the content of D-carnitine in L-carnitine products which is more accurate and sensitive.